1. Field of the Invention
This invention relates to pocket spring assemblies for cushions or mattresses, and to apparatus and methods for that manufacture.
2. Review of the Art
Pocket spring assemblies consist of two dimensional arrays of coil springs contained in individual fabric pockets. Such a construction, often known as the Marshall construction after its inventor, has for almost a century been regarded as providing a highly desirable level of cushioning performance, but usage of it has been limited because of its high cost of manufacture, involving as it does the formation of the fabric pockets, the insertion of the compressed springs and the assembly and securing of the properly oriented pocketed springs into a two dimensional array. Various efforts have therefore been made to facilitate the manufacture of such arrays, as will be found described for example in U.S. Pat. No. 4,234,983 (Stumpf) which itself represents what is believed to be the most commercially successful attempt to date to automate the construction of pocket spring assemblies. This patent discloses the production of endless strips of pocketed springs which can then be assembled into the desired arrays. Even so, such pocket spring assemblies remain costly compared to other assemblies, which whilst of lower cushioning performance, can be assembled in a more highly automated manner.